Ihsan U. Khand

Organocobalt complexes. Part II. Reaction of acetylenehexacarbonyldicobalt complexes, (R1C2R2)Co2(CO)6, with norbornene and its derivatives

Tetra- and hexa-hydro-4,7-methanoinden-1-ones and the analogous indacenediones (VIII)–(X) are formed stoicheiometrically by the title reaction or catalytically from acetylenes, norbornene derivatives, and carbon monoxide in the presence of octacarbonyldicobalt. The process leads stereoselectively to ketones of theexo-series and methyl or phenyl groups derived from the appropriate monosubstituted acetylenes are always found adjacent to the carbonyl group. The 1H n.m.r. spectra of the products are discussed and the use of an europium shift reagent together with spin decoupling is shown to allow clear distinction of the isomeric methanoindacenediones (VIII) and (IX).

Organocobalt complexes : VII. The role of butenolide complexes in the cobalt-catalysed synthesis of bifurandiones from acetylenes and carbon monoxide☆

Abstract The butenolide cobalt complexes derived from monosubstituted acetylenes are shown to be substituted in the α-position of the lactone ring. Their intermediacy in the catalytic formation of 2,6-disubstituted bifurandiones is demonstrated, and shown to require addition of both free acetylene and carbon monoxide.

Organocobalt complexes. Part I. Arene complexes derived from dodecacarbonyltetracobalt

A series of tetranuclear arenecobalt carbonyls, ArHCo4(CO)9, are formed by treating hexacarbonylacetylenedicobalt complexes, (R1C2R2)Co2(CO)6, with arenes in the presence of norbornene derivatives, or from the cobalt carbonyls Co4(CO)12 and Co2(CO)8 by direct reaction with arenes. Stable complexes are obtained from alkyl- and alkoxy-benzenes, but not from halogeno- or acyl derivatives. The spectroscopic properties of the new complexes are reported.

Organocobalt complexes. Part VIII. Specificity of the cyclopentenone synthesis from acetylenehexacarbonyldicobalt complexes and norbornene derivatives

Numerous new examples of the annelation reactions leading to cyclopentenone derivatives are reported. They provide evidence of steric control resulting in preferred substitutions at positions 2 and 5 and placement of the larger substituent at position 2 if the acetylenic precursor is disubstituted. A pathway accounting for such preference is suggested and the bulky trimethylsilyl group is utilized as a removable direction-determining group to allow synthesis of the 3- instead of 2-substituted cyclopentenones. More remote substituents in the norbornene are shown to exert a significant but no longer decisive effect, so that mixtures of isomers result. A 1H n.m.r. study has shown that the ferrocenyl substituent in 7a-ferrocenyl-3a,4,5,6,7,7a-hexahydro-4,7-methanoinden-1-one (IX) cannot rotate about the bond joining it to position 7a.

Ferrocene derivatives. Part 24. Synthesis of dihydro-2-pyrindines and dihydro-3H-2-cyclopent[c]azepines by photolysis of their cyclopentadienyliron derivatives

Bischler-Napieralski type cyclizations of N-acyl-2-ferrocenylethylamine and N-acyl-3-ferrocenylpropylamine lead respectively to cyclopentadienyl(dihydro-2-pyrindin-5-yl)iron and cyclopentadienyl(tetrahydrocyclopent[c]azepine)iron derivatives. Photolysis of their quarternary ammonium salts liberates the metal-free azabicyclic systems.

Synthesis of conjugated dienes using cobalt acetylene complexes

Unsaturated aldehydes, ketones, esters and nitriles add acetylenes in the form of their hexacarbonyldicobalt complexes to give the corresponding conjugated dienes.